Method of treating abaca cordage fiber with the hydrolysis product of methacrylato chromic chloride and product produced thereby



METHOD OF TREATING ABACA CORDAGE FREE WITH THE HYDRULYSES PRODUCT F METH- ACRYLATO CHROME CHLORIDE AND PRGD- UCI PRODUCED THEREBY George Thomson, Milton, and Chapin A. Harris, Lexington, Mass., assignors to Fabric Research Laboratories, Inc., Boston, Mass, a corporation of Massachusetts No Drawing. Application September 10, 1953, Serial No. 379,463

3 Claims. (Cl. 8-416) This invention relates to cordage, and more particularly to the modification of abaca fiber for use in cordage.

Abaca fiber, the botanical name of which is Musa textilis, is also known as Manila, or Manila hemp.

Vegetable fibers employed in the manufacture of cordage vary substantially in their physical properties. Generally speaking, the higher the tensile strength of the fiber, the lower is its elongation, which may be illustrated by a comparison between Mexican sisal (Agave fourcroya'es), also known as henequen, and abaca fiber. Thus, while Mexican sisal may exhibit a tensile strength only three-fourths that of abaca fiber, the elongation of the sisal may be twice that of the abaca. Furthermore, the knot efiiciency of Mexican sisal is commonly 1 /2 times that of abaca fiber, knot efficiency being the ratio of the tensile strength of knotted fiber to the tensile strength of unknotted or straight fiber.

By reason of its generally advantageous properties such as high tensile strength, resistance to abrasion and resistance to deterioration, and notwithstanding its relatively low elongation and knot efiiciency, abaca fiber is extensively used in cordage and is probably the most highly regarded vegetable fiber for cordage purposes.

In certain cases, considerations of economy or supply suggest the desirability of blending abaca fiber with other fiber such as Mexican sisal, for cordage purposes. As has been indicated above, sisal has lower tensile strength but higher elongation than abaca fiber. Such blending, however, has not been successful, because when the resulting cordage is subjected to tension, the stress is concentrated in the stiffer and less extensible fiber, namely the abaca fiber. The consequent non-uniform fiber stress results in unsatisfactory rope performance characteristics, including lower tensile and knot strengths.

An object of this invention is to provide abaca fiber of improved characteristics for use in cordage. Another object is to provide a method of producing such improved abaca fiber.

'In the accomplishment of the above and other objects, there is provided by this invention modified abac. fiber which exhibits permanent and marked increase of elongation, both in the dry and wet states, and yet exhibits tensile strength comparative to that of the untreated fiber. The increase of elongation may be of the order of several hundred percent; the tensile strength may be decreased somewhat, but such decease is not of practical consequence in terms of resultant cordage properties.

' In producing the modified abaca fiber of this invention, the bond between cellulose cells of the fiber and the middle lamella is relaxed, the middle lamella being the plant material which holds the cellulose cells firmly together. Additionally, cellulose cells are joined or chained sufficiently firmly to maintain high tensile strength of the fiber, and yet sufficiently loosely or slackly to permit increased elongation, the joining or chaining medium being a polymer of the hydrolysis product of methacrylato chromic chloride.

. attachment of the polymerv to cellulose cells ofthe abac.

In the practice of the invention, the relaxing of the bond between the cellulose cells and the middle lamella, and the chaining or concatenation of the cells by the polymer, may be carried out in the order desired; conveniently, however, the relaxing of the bond between the cellulose cells and the middle lamella is carried out first. In either case, in the resulting modified abaca fiber the bond between cellulose cells and the middle lamella is lax, and the cellulose cells are slackly concatenated by a polymer of the hydrolysis product of methacrylato chromic chloride.

According to a specific illustration of the invention, wherein first the bond between the cellulose cells and the middle lamella is relaxed, abaca fiber is immersed in a 12% aqueous solution of sodium hydroxide for a half hour at room temperature, after which the fiber is drained, for example as by centrifuging. The fiber is then washed with dilute (1%) acetic acid to neutralize any residual sodium hydroxide, following which the fiber is rinsed with water, and dried in air.

The action of the sodium hydroxide in the above-described treatment of the abaca fiber evidently is to swell the cellulose cells disproportionately to the middle lamella and thereby weaken or relax the bond between said cells and the middle lamella, but not to destroy said bond. In any event, the effective result is to permit markedly increased elongation of the fiber when it is subjected to tension. It should be pointed out, however, that this treatment alone is not adequate for the purposes of this invention, because of accompanying serious loss of wet strength, namely tensile strength of the fiber when in wet condition.

Continuing with the specific illustration of the invention, the chaining or concatenation of the cellulose cells in the abaca'. fiber is carried out by first immersing the fiber, previously treated with sodium hydroxide as described above, in a 0.5% aqueous solution of methacrylato chromic chloride at a pH of 4.7. This immersion is continued for a half hour, at room temperature, following which the fiber is drained, and dried in air. Then follows a polymerization step to be described hereinafter.

The structural formula of methocrylato chromic chloride may be shown as Further continuing with the specific illustration, the

fiber which has been immersed in the methacrylato chromic chloride solution and dried is then heated in an oven at 325 F. for 20 minutes. The resulting product is the modified abaca fiber of this invention.

During the immersion of the fiber in the methacrylato chromic chloride solution and the subsequent oven heat ing,-there occurs hydrolysis of the methacrylato chromic chloride, polymerization of the hydrolysis product, and

Patented Mar. 26, 1957 fiber; In other words, said cellulose cells are slackly concatenated by a polymer of thehydrolysis-product of methacrylato chromic chloride.

Modified abaca fiber produced in accordance with the above specific illustration exhibited highly' advantageous properties-for cordagc purposes. Comparison was'made with untreated abac fiber-fromthe samelot, which exhibited atensile strengthof 5.3 grams per denier and, an

elongation of- 2.3%; On' the other hand; the modified fiber exhibited-an elongation-2.8 times or 280% that of the untreated fiber, while maintaining comparative tensile strength, namely 95% that of the untreated fiber; Furthermore; the characteristics ofthe modified fiber were well maintained in the wet condition, the tensile strength being 92% of the dry modified fiber and 87% of'th'e untreated-fiber; The elongation of the'modified fiber was greater in: the wet condition, being 13 times that of'the dry modified'fiber and 3.7 times or 370% that of the untreated fiber.

it willbe understood; of course, that the invention is notlimitedtothe: details setforth above in the specific illustration. Manyvariations may be made: in carrying out the'invention, depending upon particularconditions and the results desired in individual cases; such: variations are herein suggested; Thus, in alkali metal hydroxide treatment to relax'the bond between cellulose cellsand the middlelamella of :the abaca fiber, other alkali metal hydroxides such as potassium hydroxide may be employed in place of sodium hydroxide.

In-the sodium hydroxide treatment of abac fiberdisclosed hereinabove, the concentration. of sodium hydroxide-in the aqueous solution may be varied, but generally speakingconcentrations less than 10% are inefiective, and concentrations above 15% afford no particular advantage. The temperature of the sodium hydroxide solution may vary in the general range of to 30 C. The solution at 10 C. is highly effective, but cooling is ordinarily required, and temperaturesabove 20 C. do not provide additional benefits. The time of treatment may be as short as to minutes; 20 minutes is highly-advantageous; 30 minutes is commercially a practical optimum; and generally speaking, with times substantially longer than about 30 minutes the efiectiveness of the treatment is diminished.

In the methacrylato chromic chloride treatment of the abaca fiber, which has been specifically illustrated hereinabove, the concentration of the aqueous methacrylato chromic chloride solution, in which the fiber is immersed, may vary from about 0.25% to about 1%. Concentrations above 1% are of decreasing effectiveness. The time of immersion of the fiber in the methacrylato chromic chloride solution may vary from about /2 hour, which is adequate, to over 20 hours. The pH of the solution may vary from about 3 to about 5, depending in part upon the temperature at which the fiber subsequently is to be oven-heated. Thus, if the oven-heating is to be carried out about 200 F., a solution pH of about 4 is desirable, whereas: a pH nearer 5 is advantageous: when the ovenheating is to be carried out in the range of 300 to 350 F Forthe concatenation of cellulose cells in the abaca fiber, the hereinabove-described treatment is preferred wherein the fiber is immersed in aqueous methacrylato chromic chloridesolution, and the fiber subsequently oven-heated. However, an alternative treatment with methacrylato chromic chloride may be employed. According to this alternative treatment, the dilute aqueous methacrylato chromic chloride solution, before partial neutralization, is brought to a temperature of about 200 F. and allowed to cool. Following the immersion of the fiber in the methacrylato chromic chloride solution, the fiber is dried at room temperature without subsequent oven-heating.

The-heating of the dilutemethacry-lato chromic chloridesoluti'on-appe'a'rs to bring" about orinitiate hydrolysis of the methacrylato-chromic chlorideand polymerization of thehydroly'sis product such that concatenation of cellulose- Certain of cells of the immersed fiber is accomplished at room temperature. Of course it will be understood that this alternative treatment of the fiber might still be followed, in certain instances, by oven-heating of the treated fiber.

While in the practical-accomplishment of the invention, it is preferred first to carry out the sodium hydroxide treatment of the abaca fiber, followed by the methacrylato chromic chloride treatment, these treatments may be carried out in the reverse order. in other words, as has been previously suggested, the relaxing of the bond between the cellulose cells and the middle lamella, and the concatenation of cellulose cells may be carried out in either sequence.

It will be understood that the invention may be carried out to provide, within limits, modified abaca fiber of selected increased elongation, for example, to match the elongation properties of other varieties of fiber with which it may be desired to blend the abaca fiber in the manu facture of cordage.

The utilization of modified abaca'fiber of this invention in Cordage makes possible the imparting of highly advantageous characteristics thereto, such as higher impact resistance, or as, technically known, higher energy absorption. This-characteristic is exhibited, for example, when a rope becomes taut in commencing the towing of a boat. Fiber of this invention further makes possible improved flex abrasion of cordage, exhibited in greater durability and resistance to wear; and better translation of fiber strength to cordage, because of improved distribution of stresses and relief or" stress concentration. Furthermore, by reason of the permanent modification of the fiber afforded by this invention, improvement persisting throughout repeated mechanical stressing of cordage is made possible.

It will be seen that by the present invention abaca fiber may be utilized to increased advantage in the manufacture of'cordage, an'd'effective blending of abaca fiber With fibers of other varieties may be accomplished.

It will be understood that various modifications may be made whiie'still coming within the scope of the invention.

Havingdisclosed our invention, what we claim as new and'desire to secure by 'Letters Patent'of the-United States 1s:

1. The method of producing Cordage fiber of high elongation from abaca fiber which comprisesimmersing said abaca fiber in a'10-l5% aqueous solution of an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide for about 5-30 minutes at a temperature of about 0-30 (2., draining said fiber, neutralizing residual alkali and washing said fiber with Water, drying said fiber, immersing said fiber in a 0.25-1 Water solution of methacrylato chromic chloride ofpH about 35 at room temperature for about /2 20-h0l1rS, drain ing said fiber and'drying it, and heating the thus-treated fiber at about 300350 F. fora time inthe neighborhood of 20' minutes.

2. As a new and useful product, cordage fiber of. high elongation produced from abaca-fiber by immersing said abaca fiber in a l015% aqueous solution of an alkali selected from the groupconsistingof sodium hydroxide and potassium hydroxide for about 5-30 minutes at a temperature of about 030 C., draining said fiber, neutralizing residual alkali and washing said fiber with water, drying said fiber, immersing said fiber in a 0.254% water solution oi methacrylato chromic chloride of pH about 35- at room temperature for about /220 hours, draining said fiber and drying it, and heating the thus-treated fiber at about 300350 F. for a time in the neighborhood of 20 minutes.

3. The method of producing cordage fiber of high elongation from abaca fiber which comprises immersing said abaca fiber in a 12% aqueous solution of sodium hydroxide for about one-lialfhjour at roomtemperature, draining said fiber, neutralizing residual sodium hydroxide with acetic acid and washing said fiber with water, drying said fiber, immersing said fiber in a 0.5% water solution of methacrylato chromic chloride of pH about 4.7 at room temperature for about one-half hour, and heating the thustreated fiber at 325 F. for 20 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,273,040 Iler Feb. 17, 1942 OTHER REFERENCES Textile Research Journal, October 1951, pp. 740446, (Copy in P. O. Libr.) 

1. THE METHOD OF PRODUCING CORDAGE FIBER OF HIGH ELONGATION FROM ABACA'' FIBER WHICH COMPRISES IMMERSING SAID ABACA'' FIBER IN A 10-15% AQUEOUS SOLUTION OF AN ALKALI SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE AND POTASSIUM HYDROXIDE FOR ABOUT 5-30 MINUTES AT A TEMPERATURE OF ABOUT 0-30*C., DRAINING SAID FIBER, NEUTRALIZING RESIDUAL ALKALI AND WASHING SIAD FIBER WITH WATER, DRYING SAID FIBER, IMMERSING SAID FIBER IN A 0.25-1% WATER SOLUTION OF METHACRYLATO CHROMIC CHLORIDE OF PH ABOUT 3-5 AT ROOM TEMPERATURE FOR ABOUT 1/2-20 HOURS, DRAINING SAID FIBER AND DRYING IT, AND HEATING THE THUS-TREATED FIBER AT ABOUT 300-350*F. FOR A TIME IN THE NEIGHBORHOOD OF 20 MINUTES. 